You can get a mosquito bite in the winter, although it is unusual in regions with consistently freezing temperatures. In temperate climates, insect populations disappear, leading many to believe they die off when cold arrives. However, certain species have developed biological strategies to persist through the winter months. Specific environmental factors can interrupt this dormant state, leading to unexpected activity and the possibility of a winter bite.
How Mosquitoes Survive the Cold (Diapause)
Mosquitoes disappear during cold weather due to diapause, a state of suspended animation. This physiological response to cues like shortening daylight hours involves a deep metabolic slowdown and hormonal changes. Diapause halts development, making the insects highly resistant to freezing.
The specific life stage entering diapause varies widely. Aedes genus mosquitoes survive winter as cold-resistant eggs deposited in soil or dried containers. Culex and Anopheles species overwinter as mated adult females. These females find protected microhabitats after obtaining the necessary blood meal.
During diapause, metabolism slows, pausing development until warmer weather triggers resumption. These dormant insects are not seeking blood meals, which is why the biting threat disappears below 50°F. Surviving adult females emerge first in the spring, ensuring a rapid start to the biting season.
The Species That Bite Indoors
Winter bites are almost always caused by individuals that have sought shelter indoors. Certain species, often called “house mosquitoes,” have adaptations allowing them to survive the cold season in human structures. These include species like Culex pipiens, which sometimes appears as Culex pipiens molestus in urban environments.
These sheltered adult females find refuge in places with stable, above-freezing temperatures, such as basements, crawlspaces, and utility tunnels. They remain inactive until warmth and an available host cause them to stir. If the environment stays above 50°F, and they detect a host’s carbon dioxide or heat, they may briefly awaken to feed.
A person might receive a bite indoors even when the outdoor temperature is below freezing. This activity is not a sign of an active outdoor population, but a localized, indoor problem from a few individuals. Females inside homes may also find small sources of standing water, allowing them to lay eggs and complete their life cycle indoors.
Environmental Factors That Trigger Winter Bites
Unseasonal warm spells are the most common environmental factor temporarily triggering winter biting activity. When outdoor temperatures rise above the 50°F to 55°F threshold for a few consecutive days, dormant mosquitoes can be briefly roused from their overwintering sites. These insects may emerge from sheltered areas to seek a blood meal, mistakenly sensing that spring has arrived.
Climate change contributes to an extended mosquito season, making late-season and early-season bites more likely. Warmer winters allow populations to survive and remain active for longer periods. Furthermore, artificial light pollution can interfere with the physiological signals that induce diapause. Studies suggest females exposed to dim light at night may fail to enter dormancy and remain reproductively active, leading to extended biting behavior.